2,4-D, a phenoxyalkanoic acids herbicide, is a selective systemic hormone herbicide. Pure 2,4-D exists as white crystals, which has low solubility in water but is easily soluble in organic solvents such as ethanol and benzene. The amine salts and sodium salts of 2,4-D, however, are quite easily soluble in water. 2,4-D is strongly systemic. At low concentration, 2,4-D can inhibit the growth and development of the plant and cause uncontrolled growth and eventually death. 2,4-D is mainly used for post-emergence foliar treatment and has various effects on the synthesis of nucleic acids and proteins, such that the growing points of the plant stop growing, young leaves are inextensible and normal photosynthesis is inhibited. When transported to the lower parts of the plants, 2,4-D can promote uncontrolled cell division. Root tips become swollen, losing the ability of absorption. Stems and stalks become distorted and aberrant. Sieve tubes are blocked and the phloem is damaged, such that the transport of organic substances is obstructed, leading to the death of the plant. 2,4-D herbicide has an outstanding control efficiency on annual or perennial Poaceae weeds and some broadleaf weeds in fields of soybean and other Fabaceae plants, for example, such weeds as amaranth, knotweed, lamb's-quarters, night shade, siberian cocklebur, barnyard grass, foxtail grass, digitaria sanguinalis, broomcorn millet and the like.
The main formulations of 2,4-D are emulsifiable formulation of its esters and aqueous formulation of its salts. Because the organic solvents in the emulsifiable formulation are flammable and would cause great pollution to the environment, the fraction of such formulation among herbicide formulations has been decreasing annually in recent years. Although aqueous formulation of 2,4-D salt is environment-friendly, the aqueous formulation with high concentration is very easy to crystallize at low temperatures, and the aqueous formulation with low concentration, while easy to crystallize, will lead to increased costs in packaging and transporting, which limits the use of aqueous formulation of 2,4-D salt to some extent.